DE1097429B - Process for the production of low molecular weight acetone dicarboxylic acid dialkyl esters - Google Patents

Description

The invention relates to a new process for the preparation of lower alkyl esters of acetone dicarboxylic acid in particularly high yield using special extraction agents. The esters are suitable as Catalysts for the polymerization of chlorinated rubber.

In the patent application P 20482 IVb / 12 o (German Auslegeschrift 1 092 900), among other things, the production of low molecular weight acetone dicarboxylic acid dialkyl ester is described, whereby citric acid is treated at about 40 to 65 ° C with sulfuric acid at a concentration of more than 95%, the reaction mixture either sulfur trioxide or "Oleum" is gradually added and then a primary alkanol is added. The reaction is continued at about 25 to 45 ° C until substantial amounts of the ester have formed. The ester is characterized recovered from the strongly acidic reaction mixture, that one pours the mixture maintaining a p _H -value of about 1.5 to 6 in ice-water and the ester is then extracted with benzene. The Pj ₁ value within the specified range is maintained by adding the strongly acidic reaction mixture and an alkaline agent, preferably ammonia, simultaneously to a mixture of ice and water, a low temperature, e.g. B. less than 20 ° C is complied with. The partial neutralization of the strongly acidic reaction mixture as a result of the addition of an alkaline agent generates considerable heat which is generated by the addition of ice in connection with external cooling, e.g. B. by means of a saline solution, must be derived. This method is costly because it requires large amounts of ice and special equipment. The cost of the process is also markedly increased by the use of the alkaline agent.

It has now been found that, surprisingly, the use of certain extractants is the additive of the alkaline agent and the costly dissipation of heat. Besides, that's the way it is The yield achieved is higher than that previously used for the production of lower alkyl esters of acetone dicarboxylic acid from citric acid procedures used. Such solvents are chlorinated alkanes with up to 5 carbon atoms, such as chloroform, ethylene dichloride, tetrachloroethane, 1,1-dichloroethane, 1,5-dichloropentane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1,1,2-tetrachloroethane or 1,2,3-trichloropropane. The ones that can be achieved with them excellent yields and preferred solvents because of their technical availability are chloroform, ethylene dichloride and tetrachloroethane.

After extraction with one of these solvents, this z. B. by distillation under reduced Pressure removed. The residue obtained consists of a lower alkyl ester of acetone dicarboxylic acid, its degree of purity for most manufacturing uses

low molecular weight acetone dicarbon

dialkyl ester

Applicant:

Chas. Pfizer & Co., Inc.,
Brooklyn, NY (V. St. A.)

Representative: Dr. W. Beil and A. Hoeppener, Lawyers, Frankfurt / M.-Höchst, Antoniterstr. 36

Claimed priority:
V. St. v. America January 17th and July 17th, 1958

Edgar Kindon Hamilton, Merrick, N.Y.,

and George Lukacs, Riverdale, N.Y. (V. St. A.),

have been named as inventors

purposes is sufficient. If a product of higher purity is desired, the residue is sub-fractionated reduced pressure. If appropriate, the organic solution containing the ester can also be washed with water and then dried over an anhydrous drying agent such as anhydrous sodium sulfate before evaporating in vacuo.

The extraction can be carried out by any of the known methods. Under certain conditions can it may be useful to use a batch process in which the extractant with the Reaction mixture is treated with stirring, whereupon the layers are separated. Such a procedure however, it is generally not used because some solvents have a number of separate ones Extractions may be necessary and this is technically too cumbersome. To the amount of costly To minimize the extraction agent, it is preferred to use a continuous countercurrent process at. Any of the technical processes known for this purpose, e.g. B. a so-called “Podbielnak extractor” (cf. UlImann, “Encyklopädie der technical chemistry ", 3rd edition, vol. 1 [1951], p. 425). Of course, the

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the solvents used at the temperature used - higher or lower temperatures are used,

ratur be liquid. The preferred temperature range is between about

The selective effect of the individual extractants 15 and about 25 ° C.

is explained in more detail below: Six 100 cc samples Example 1
with a content of 21 g acetone dicarboxylic acid di 5

methyl esters were produced. A sample was sive with a 1131 glass-lined vessel benzene, the other with hexane and the remaining was washed with 41.7 kg with 98 to 99 ° / ₀ sulfuric acid be-chlorobenzene, trichlorethylene, chloroform and ethylene sends and Heated to 55 ° C. Dichloride was extracted without stirring. It was found that 18.12 kg of anhydrous granular citric acid was added. Benzene 5.6 g of the ester, 0.4 g with hexane and 0.4 g with chlorine g were extracted. This shows started. 13.231 oleum, the 20 ° / ₀ sulfur trioxide contained the clear superiority of the chloroform and Äthylendi-, were then washed with a speed of chloride. Similarly poor results were added at approximately 0.3781 per minute. The temperature of other non-halogenated aliphatic or J-5 was kept at a similarly good 50 to 55 ° C. for 1 hour after the addition of oleum had started. Then the mixture was cooled to results with other aliphatic chlorinated hydrocarbons - 35 ° C and added 30.241 anhydrous methanol, substances such as tetrachloroethane and 1,1-dichloroethane, achieved. The temperature was then raised to 33 bis for 3 hours

The temperature at which the extraction was carried out was maintained at 37 ° C and then decreased to 25 ° C,

is not decisive, but it is known that a 20 To obtain the acetone dicarboxylic acid dimethyl

Solvent at higher temperature generally esters the reaction mixture four times with each

more dissolving than lower. Thus, at the ex-681 chloroform extracted, and the extracts were

Execution of the method according to the invention each temperature combined. The chloroform solution was then with 681

Temperature between about 5 ° C and the boiling point of water and washed over anhydrous sodium sulfate

Solvent can be applied. Most conveniently 25 dried. The desiccant was stripped off and

the extraction is carried out at room temperature. the solvent is distilled off at atmospheric pressure.

Since the work was also carried out at a relatively high temperature, the crude ester obtained as a residue was again

can be, it is not always necessary to convert the distilled, the ester at a pressure of 10 mm

cool mixture before extraction. The required at 125 ° C passed. The pure product, based on the

the amount of extractant depends on the 30 citric acid that was obtained in a yield of 75% of the

Distribution coefficient of the ester obtained in the selected theoretical amount.

Solvent off. This can easily be determined beforehand _π . . . "

will. Example 2

The yield that can be achieved according to the invention is very high. A reaction vessel with a capacity of 11341 was used

It is consistently 70 ° / ", based on the original 35 294.45 kg 96 ° / ₀ sulfuric acid were charged and 55

used amount of citric acid, sometimes even 75 ° / _0th heated to 6O ^{0 C.} A total of 135.9 kg of citric acid

This represents a significant increase over after being inflicted within 15 to 20 seconds. at

previous process achievable yields. One of these reactions develops very violently carbon oxide,

Another significant advantage of the invention is that it can form an explosive mixture with oxygen.

As already mentioned, the process consists in the fact that the partial 40

wise neutralization and cooling to be flushed with nitrogen before extraction of the citric acid. the

not applicable. Implementation is to be carried out under such conditions,

It was further found that by adding that the evolving gas can easily escape.

Water before extraction with the chosen solution. About 5 minutes after adding the citric acid

medium significantly increases the effectiveness of the process 45 while maintaining a temperature of 50 to 55 ° C

will. The addition is not essential, however, 178.9 kg "oleum", containing 20 ° / ₀ sulfur trioxide,

advantageous, since this adds the necessary to achieve comparable. The addition took place within 50 minutes.

Yields required amount of solvent down- Then the reaction mixture was left for an additional 10 minutes

is set. The amount of water to add depends on standing and then cooling it to about 35 ° C.

of the equipment used and at a speed of 5 ° This mixture was 151.21 of methanol with such

with which the water is added. Without a particular speed that the temperature is added between

Plant that a rapid addition of water and a 33 and 37 ° C remained. The mixture was in a with

Rapid dissipation of heat is made possible by the stainless steel vessel provided with a propeller agitator

Hydrolysis of the ester is prevented, one achieves in steel treated with 15121 ethylene dichloride, the organic

generally with a water addition of about 10 to 55 niche layer and the extraction again

about 40, preferably about 20 percent by weight, based on a further 15,121 ethylene dichloride repeated. To

on the reaction mixture, favorable yields. Yet union of organic extracts and removal

larger amounts of water can also be used with advantage, until the solvent in vacuo gives the acetone

200 percent by weight, can be used. dimethyl dicarboxylate with a b.p. _lo = 123 to 125 ° C

Each ester in an aqueous medium is in counter 60 in approximately 70 ° / ₀ yield, based on the amount

was an acid catalyst even with a relatively large amount of citric acid,

hydrolyzed at low temperature. The extent of the. .

Hydrolysis depends on the contact time between ester example ό

and hydrolyzing medium. For the invention it was used with the same amounts and under the

For the purposes of this, the use of relatively high 65 same conditions as in Example 2 is used

Temperatures, even up to 100 ° C, are possible if the only difference is the addition of citric acid

Extraction was carried out immediately after adding the water to the sulfuric acid within 25 to 30 seconds,

he follows. In the commonly available The reaction mixture were 151.21 of methanol such as

Systems, it is appropriate to add the temperature to about 10 in Example 2 and the mixture is now in a up to about 40 ° C, but you can also considerably 70 Podbieliuak centrifugal extractor, model 6900, with a

Introduced at a rate of 5.671 per minute with the simultaneous addition of tetrachloroethane at a rate of 15.121 per minute. The solvent was then distilled off in vacuo and the residue was distilled at a pressure of 10 mm Hg, the ester passing over at 123 to 125.degree. Yield 70 ⁰ I ₀ of dimethyl ester.

Example 4

A 3000 cc Synthesis, provided with a ground-in stirrer, a dropping funnel and a condenser fitted with a hood effective three-necked round bottom flask was charged with 600 cc of 98 to 99 ° / ₀ sulfuric acid and heated to 65 ° C. The addition funnel was removed and 480 grams of anhydrous granular citric acid was quickly added and the flask was re-fitted with the addition funnel. After 3 minutes, the stirrer was started and 340 ecm of "oleum" containing 20% sulfur trioxide was added over the course of 30 minutes. The reaction mixture was held at 49 to 52 ° C. for 1 hour after the addition of "oleum". The mixture was then cooled to 40 ° C., 400 ecm of anhydrous methanol were added and the temperature was kept at 35 to 37 ° C. for 2 hours.

The reaction mixture was extracted four times with 1.5 liters of 1,1-dichloroethane each time, the extracts were combined, washed with water using a quarter of the extract volume of water, and the layers separated. The organic layer was dried over anhydrous sodium sulfate, the drying agent filtered off and the filtrate distilled in vacuo, leaving the desired product in crude form as a residue received. Yield 70% dimethyl ester.

Example 5

The procedure was initially as in Example 2 and about 5 minutes after the addition of the citric acid to the sulfuric acid, 36.24 kg of sulfur trioxide were added within 45 minutes. The temperature of the mixture was kept during the addition and for a further 35 minutes at 50 to 55 ° C then decreased to 25 ⁰ C. 151.21 of methanol were then added at such a rate that the temperature remained between 25 and 35 ° C., and the mixture was then extracted with ethylene dichloride as in Example 2. Yield of dimethyl ester about 65%; Kp. _Lo = 125 ° C.

speed of 5.671 per minute with the simultaneous addition of 11.341 tetrachloroethane per minute in a Podbielniak centrifugal extractor, model 6900, introduced and then worked up as usual. Yield 70 ° / ₀ .

Example 8

A reaction mixture obtained according to Example 4 were fed to 700 cc of water at such a rate that a temperature was maintained * of 15 to 2O ⁰ C. The mixture was then extracted four times with 11 1,1-dichloroethane each time. The extracts were worked up as in Example 4 and as there obtained a yield of 70 ° / _0th This yield was also obtained if, instead of 700 ecm of water, 800 ecm of water were added to the reaction mixture before the extraction.

Example 9

A product obtained according to Example 4 reaction mixture was cooled to 15 ° C and mixed while maintaining a temperature of 15 to 20 ^0C with 250 cc of water.

It was then extracted four times with 11 1,1-tetrachloroethane each time. The extracts were worked up as in Example 4, followed by, based on the amount of citric acid, 65 ° / ₀ of the theoretical amount obtained diester.

Example 10

A reaction mixture obtained in Example 2 was allowed to stand for 30 minutes and then cooled to about 15 ° C. Water was added in a total amount of 1891 so that the temperature remained between 15 and 20 ° C. The mixture was then introduced into a tank provided with a propeller agitator and containing 945 liters of ethylene dichloride. The mixture was stirred for 2 hours and the phases were allowed to separate. The organic layer was drawn off and extracted again with 945 liters of ethylene dichloride. After removal of the solvent in vacuo the desired product was obtained in a yield of about 70 ° / ₀ of the theoretical amount, based on the citric acid used.

The comparison of Examples 7 to 10 with Examples 1 to 6 shows that the addition of water to Reaction mixture before the extraction, the use of smaller amounts of extractant to achieve the enables equal yields.

Example 6

A reaction mixture obtained as in Example 5 was introduced into a Podbielniak centrifugal extractor, model 6900, at a rate of 5.671 per minute with the simultaneous addition of tetrachloroethane at a rate of 15.121 tetrachloroethane, then the solvent was removed from the extractor in vacuo and the residue is distilled at a pressure of 10 mm Hg, the ester passing over ^{at 123 to 125 ° C.} Yield 70 ° / ₀ .

Example 7

A reaction mixture obtained according to Example 3 was added 151.21 of methanol in such a way that a Temperature of 33 to 37 ° C was maintained, the reaction mixture was allowed to stand for a further 30 minutes and then cooled it down to around 15 ° C. 113.41 were water now added so that the temperature remained between 15 and 25 ° C. The mixture was then

Claims (3)

PATENT CLAIMS: 1. A process for preparing low molecular weight dialkyl esters of acetonedicarboxylic acid, characterized in that the of citric acid by the action of more than 95 ° / ₀ sulfuric acid and "oleum" or sulfur trioxide at 40 to 65 ° C and subsequent esterification obtained with a low molecular weight alkanol reaction mixture the ester is removed by extraction with an aliphatic chlorinated hydrocarbon with up to 5 carbon atoms. 2. The method according to claim 1, characterized in that the extractant used is chloroform, Ethylene dichloride or tetrachloroethane is used. 3. The method according to claim 1, characterized in that the reaction mixture before the Extraction Add water in an amount of about 10 to 40% based on the weight of the reaction mixture. © 009 699/492 1.61